Step-by-step explanation:
The approximate tip is - 12.30$
Because bill is 81.79$
and tip - 15%
therefore bill amount divided by 15/100
==> 81.79* 15% is 12.30$
Let the equal sides of the isosceles Δ ABC be x.
Given that the perimeter of Δ ABC = 50m.
Therefore, 2x + AC = 50 --- (1)
It is also given that the perimeter of Δ ABD = 40m.
Therefore, x + BD + AD = 40
BD is the median of the Δ ABC. Therefore, D is the midpoint of AC.
So AD = CD.
Or, AD =
AC
Therefore, 
Multiply both sides by 2.
2x + 2BD + AC = 80
From (1), 2x + AC = 50.
Therefore, 2BD + 50 = 80
2BD = 80 - 50
2BD = 30
BD = 15m.
I believe 3m 7cm 3cm= 13 meters :).
I think that B is the most logical answer.